The present invention relates to audio magnetic tape cassettes, and more particularly, to a compact cassette the same as or smaller in size than a standard "Phillips" type compact cassette.
Recently, cassette tape recorders have been reduced in size and in weight, and accordingly magnetic tape cassettes have been also miniaturized. Therefore, there has been a strong demand for the provision of small magnetic tape cassettes which are suitable for high-quality and high-density recording and reproducing operations. For instance, the magnetic tape cassette should be suitable for use in digital recording such as with PCM (pulse code modulation) whereby recording and reproducing operations are carried out with input signals converted into pulse signals. In such a system, the recording frequency bandwidth must be about five times as wide as the maximum bandwidth of a conventional audio tape intended for analog recording. Therefore, video tape cassettes, which are considerably larger in size than audio compact cassettes, have been extensively employed for such purposes.
Video tape cassettes (except for special cases) are intended for use with a rotary head system. These video tape cassettes have guard panels which close openings formed in the front parts of the cassettes and are swingable upwardly for recording and playing back. That is, in video and digital systems because the recording and reproducing operations are carried out using higher recording densities and wider bandwidths than is possible with a conventional audio compact cassette, and because the tape is therefore more sensitive to contamination, it is necessary to more positively prevent the entrance of dust and the like into the cassette to protect the magnetic tape from damage.
The technical concept of the invention is applied to a very small magnetic tape cassette which, similar to the above-described video tape cassette, employs a relatively wide frequency bandwidth recording and reproducing system, and which is applicable to audio devices, and is the same as or smaller in size than the conventional audio compact cassette. Specifically, so that the cassette can be used outdoors and carried without a storage casing, the magnetic tape cassette must have better dust protection than a conventional video tape cassette.
A variety of digital audio tape magnetic tape cassettes have been proposed. Such magnetic tape cassettes generally include a guard panel which is swung upwardly, similar to the above-described video tape cassette, and a slide guard which is slid along the bottom of the cassette in a direction perpendicular to the longitudinal direction of the cassette, thereby to close the lower part of an opening formed in the front part of the cassette to receive the tape drawing mechanism of the magnetic tape recording and reproducing device.
As is apparent from the above description, it is desirable that the above-described digital audio type magnetic tape cassette having the guard panel and the slide guard provide more positive protection of the magnetic tape, namely, a more positive dust-proofing action than the conventional video tape cassette. Especially, there has been a demand for a magnetic tape cassette whose slide guard is more smoothly operable.